Just a thought but did you specifically ask the builders to ensure the roof was strengthened sufficiently to allow you to safely use it for planting and to walk on? You mention it’s “as strong as a house roof” but the standard structure for a flat roof isn’t built to take a huge amount of direct weight.
You can get roof-garden composts which are designed to be moisture retaining whilst remaining lightweight.
If your aim is to visually loose the shed roof then using plants that link into the planting in the adjacent border will help it merge together. This could be using the same type of plants or ones with similar form/colour.
If the shed roof is very visible from the house, I think I would probably go for a green roof system rather than pots. You can get sedum (and other plant) mixes for shade from most of the main suppliers.
If you have a garden and a library, you have everything you need.”—Marcus Tullius Cicero East facing, top of a hill clay-loam, cultivated for centuries (7 years by me). Birmingham
If you really want a living roof, I'd be interested to know why you've decided against going down the sedum / other succulent route. That would give you a very low maintenance, year round, tapestry of subtle colours.
I think bright green fake grass in that location would always look artificial and agree with others that pots are definitely not a low maintenance option unless they are planted with succulents that require little water.
If your main view of the shed is from the angle the photo is taken, I agree with Fairygirl that putting a proper edging or perhaps a simple, low safety fence along the area you were thinking of decking and then planting up the area in front of it with year round interest shrubs will soon detract from the structure. It's just 'right there' at the moment. If you only see glimpses of it through a shrub border you'll not really notice it any more.
Heaven is ... sitting in the garden with a G&T and a cat while watching the sun go down
Some brilliant comments here. The roof is very, very strong consisting of 6x2 rafters as used in commercial projects. I sort of went away from the sedum idea when it was clear I hadn’t taken everything into account. I know I’m asking for a lot and again I didn’t really take watering into account. I don’t mean to sound ignorant or flippant here but how is it that certain weeds, Ivy etc continue to grow in my garden with no intervention/watering/care from anyone? How can these b*ggers flourish with no help?
They thrive because they have extensive root systems that can access water from a wide area. In an unwatered pot they would die just like most other plants.
If you were to plant ivy, it would need watering until it got established. The ones that grow from seeds that the birds drop seem to thrive all on their own, but it's probably only a tiny proportion of the seeds that make it to maturity, the ones that fall in a suitable place and get enough water from rain (or byproduct of gardeners watering other things).
Doncaster, South Yorkshire. Soil type: sandy, well-drained
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You can get roof-garden composts which are designed to be moisture retaining whilst remaining lightweight.
If your aim is to visually loose the shed roof then using plants that link into the planting in the adjacent border will help it merge together. This could be using the same type of plants or ones with similar form/colour.
If the shed roof is very visible from the house, I think I would probably go for a green roof system rather than pots. You can get sedum (and other plant) mixes for shade from most of the main suppliers.
East facing, top of a hill clay-loam, cultivated for centuries (7 years by me). Birmingham
I think bright green fake grass in that location would always look artificial and agree with others that pots are definitely not a low maintenance option unless they are planted with succulents that require little water.
If your main view of the shed is from the angle the photo is taken, I agree with Fairygirl that putting a proper edging or perhaps a simple, low safety fence along the area you were thinking of decking and then planting up the area in front of it with year round interest shrubs will soon detract from the structure. It's just 'right there' at the moment. If you only see glimpses of it through a shrub border you'll not really notice it any more.